Hearing aids are electronic instruments that compensate for hearing losses by amplifying sound. The electronic components of a hearing aid include a microphone for receiving ambient sound, an amplifier for amplifying the microphone signal in a manner that depends upon the frequency and amplitude of the microphone signal, a speaker for converting the amplified microphone signal to sound for the wearer, and a battery for powering the components. Hearing aids may also be equipped with a telecoil. A telecoil (also referred to as a T-coil for “telephone coil”) is a small device installed in a hearing aid that detects the electromagnetic field generated by audio induction loops such as the speaker of a telephone handset. The signal detected by the T-coil is processed and converted to an acoustic signal by the speaker. When the hearing aid is in the telecoil mode, the processing of the T-coil signal may be performed in place of, or in addition to, processing of the microphone signal to generate sound for the hearing aid wearer.